High-resolution structure of the Shigella type-III secretion needle by solid-state NMR and cryo-electron microscopy.Demers, J.P., Habenstein, B., Loquet, A., Kumar Vasa, S., Giller, K., Becker, S., Baker, D., Lange, A., Sgourakis, N.G.
(2014) Nat Commun 5: 4976-4976
- PubMed: 25264107
- DOI: https://doi.org/10.1038/ncomms5976
- Primary Citation of Related Structures:
- PubMed Abstract:
We introduce a general hybrid approach for determining the structures of supramolecular assemblies. Cryo-electron microscopy (cryo-EM) data define the overall envelope of the assembly and rigid-body orientation of the subunits while solid-state nuclear magnetic resonance (ssNMR) chemical shifts and distance constraints define the local secondary structure, protein fold and inter-subunit interactions. Finally, Rosetta structure calculations provide a general framework to integrate the different sources of structural information. Combining a 7.7-Å cryo-EM density map and 996 ssNMR distance constraints, the structure of the type-III secretion system needle of Shigella flexneri is determined to a precision of 0.4 Å. The calculated structures are cross-validated using an independent data set of 691 ssNMR constraints and scanning transmission electron microscopy measurements. The hybrid model resolves the conformation of the non-conserved N terminus, which occupies a protrusion in the cryo-EM density, and reveals conserved pore residues forming a continuous pattern of electrostatic interactions, thereby suggesting a mechanism for effector protein translocation.
1] Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany  Department of Molecular Biophysics, Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany  Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany.